The present invention relates to an analog computer variable duty modulator used in an air conditioning and heating system in a controlled area wherein the compressor off time in a cycle is fixed and the operating time of the compressor is adjusted automatically in response to the difference between the ambient temperature and selected ON and OFF temperatures.
Controls, such as thermostats and timers, for air conditioning and heating systems are widely used in residential and commercial applications. Thermostats work on a single function based on temperature. Timers work on a single function based on time. For both thermostats and timers the equipment is either on or off. The thermostat works on the basis of temperature sensing. The on and off time of the compressor is random and is subject to a range of temperature variations. The timer works on the basis of a fixed total period of time, i.e., the ON and OFF time functions in such a way that the addition of the two equals a constant time period. This procedure can control the temperature but with relatively high peaks and valleys when compared to the thermostat. In the cooling mode, for both types of controls, when the OFF time is excessively long, on the order of 10 to 15 minutes, the temperature rises and the relative humidity increases. When the compressor starts, it must run longer because it needs to condense the moisture first before room temperature is lowered. The present invention reduces the negative feature of relative humidity build up and creates the opportunity for energy savings.
Some thermostats and timers are controlled by microprocessor based digital circuitry. They are subject to strong electromagnetic interference generated by seasonal electrical storms or incoming noise via the power lines or the outgoing lines that connect the cycler to the controlled devices. This causes memory loss, false processing of transients and distorted programs. All of this provokes the failure of the cycler, in most cases producing permanent damage to the delicate CMOS chips. The present invention of analogic nature makes it completely noise immune.
None of the commercial cyclers analyzed has the provision, in the case of failure, that allows the user to return to the original thermostat or manual operation of the air conditioning and heating equipment without making changes in the wiring or calling for a trained technician.
Controlled residential devices studied lack the multifeatured capability of being used on commercial equipment over 5 tons, on heat pumps without additional wiring, programmed fan delay, a remote sensor location and an auxiliary output for control of secondary equipment.